Gattendorfia schmidti, Korn & Weyer, 2023

Korn, Dieter & Weyer, Dieter, 2023, The ammonoids from the Gattendorfia Limestone of Oberrödinghausen (Early Carboniferous; Rhenish Mountains, Germany), European Journal of Taxonomy 882, pp. 1-230 : 126-130

Gattendorfia schmidti sp. nov.

urn:lsid:zoobank.org:act:7AE42990-A874-40D5-998E-5D9DC76284E2

Figs 74–75 ; Tables 72–73

Gattendorfia subinvoluta – Schmidt 1924: 151, pl. 8 figs 7–8; 1925: 535, pl. 19 fig. 8.

Gattendorfia tenuis – Vöhringer 1960: 153, pl. 5 fig. 6, text-fig. 38. — Weyer 1965: 447, pl. 6 fig. 1. — Bartzsch & Weyer 1986: pl. 2 fig. 2. — Korn 1994: 75, text-figs 65b, 66g, 67d, 68b; 2006: textfig. 3i.

Gattendorfia involuta – Becker in Becker et al. 2021: 409.

Diagnosis

Species of Gattendorfia with a conch reaching 70 mm diameter. Conch at 5 mm dm thinly discoidal, very evolute (ww/dm ~0.40; uw/dm ~0.60); at 15 mm dm thickly discoidal, evolute (ww/dm ~0.50; uw/ dm ~0.45); at 40 mm dm thickly discoidal, subinvolute (ww/dm ~0.50; uw/dm ~0.25). Whorl profile in the juvenile stage depressed oval, at 40 mm dm circular (ww/wh ~1.00); coiling rate moderately high (WER ~1.85). Venter broadly rounded throughout ontogeny, umbilical margin narrowly rounded in the adult stage. Growth lines lamellar, wide-standing, with concavo-convex course. Deep constrictions on the shell surface and prominent internal shell thickenings. Suture line with lanceolate, very weakly pouched external lobe and V-shaped adventive lobe.

Etymology

Named after Hermann Schmidt (1892–1978) in appreciation of his studies on the Devonian– Carboniferous boundary.

Material examined

Holotype

GERMANY • Rhenish Mountains, Oberrödinghausen , railway cutting; Hangenberg Limestone , bed 1; Vöhringer Coll.; illustrated by Vöhringer (1960: pl. 5 fig. 6), Korn (1994: text-fig. 65b) and Korn (2006: text-fig 3i); re-illustrated here in Fig. 74A ; GPIT-PV-63952.

Paratypes

GERMANY • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 1; Vöhringer Coll.; GPIT-PV-63951 • 1 specimen; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 2; Vöhringer Coll.; GPIT-PV-63882 • 3 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 2; Vöhringer Coll.; MB.C.31156.1–3 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3c; Vöhringer Coll.; MB.C.31157.1–2 • 2 specimens; Rhenish Mountains , Oberrödinghausen, railway cutting; Hangenberg Limestone, bed 3a; Weyer 1993–1994 Coll.; MB.C.31158.1–2 .

Description

Holotype GPIT-PV-63952 is a moderately preserved specimen with a 56 mm diameter of the conch. A part of the aperture is broken off, so that the illustration shown here ( Fig. 74A ) seems to figure a smaller specimen than that shown by Vöhringer (1960: pl. 5 fig. 6). The specimen is, at 40 mm diameter, thickly discoidal and subinvolute (ww/ dm = 0.47; uw/dm = 0.23) with a moderately high coiling rate (WER = 1.84). The umbilical margin is quite distinct and separates the almost vertical umbilical wall from the evenly convex flanks, which converge to the continuously rounded venter.

Only small shell remains are preserved on the holotype. It can be assumed that the growth lines extend parallel to the prominent constrictions, which are arranged at 90 degrees. These run in an almost straight line across the flank, forming a low ventrolateral projection and bending back to form a deeper ventral sinus ( Fig. 75D ). The suture line is typical of Gattendorfia and has a lanceolate external lobe with weakly curved flanks and a weakly asymmetrical, narrowly V-shaped adventive lobe ( Fig. 75C ).

The cross sections of paratypes MB.C.31156.1 and MB.C.31157.2 show the ontogenetic development of the conch up to a diameter of 23 mm ( Fig. 75A–B ). Both show very evolute inner whorls; the uw/dm ratio ranges from 0.55 to 0.60 between 2 and 8 mm conch diameter. Later in ontogeny, the whorls start to overlap the preceding whorl more strongly and already at 23 mm diameter, the uw/dm ratio has decreased to a value of ~0.33. Paratype MB.C.31156.1 shows, at this diameter, already the transformation of the broad-oval whorl profile of the juvenile stage into the adult stage with a distinctly pronounced umbilical margin.

Remarks

The specimen chosen here as the holotype of the new species Gattendorfia schmidti sp. nov. was already determined by Becker (in Becker et al. 2021) as the neotype of the species “ Gattendorfia involuta Schindewolf, 1924 ”. However, this determination seriously complicated the problematic nomenclatorial circumstances of that species. For this reason, it is necessary to review and discuss the course of the research history concerning the species “ Gattendorfia involuta ”.

In his brief discussion of the ammonoid occurrences of Saalfeld in Thuringia, Schindewolf (1924: 105) stated that he distinguished three species of Gattendorfia , namely G. subinvoluta and the two new species G. ventroplana and G. involuta . However, he has described and illustrated only G. ventroplana ( Schindewolf 1923: 409, pl. 16, fig. 10, text-fig. 14b), although under the species G. subinvoluta . For the third species G. involuta he provided only a brief, uninformative definition: “ G. involuta nov. sp., eine gegenüber G. subinvoluta flacher scheibenförmige, enger genabelte und hochmündigere Spezies.” = “ G. involuta nov. sp., a species more thinly discoidal, more closely umbilicate and more high-apertured than G. subinvoluta .” Schindewolf did not explain where the material of “ G. involuta ” came from; however, it is very likely that it either came from Gattendorf or Saalfeld. It is important to mention that at that time Schindewolf still held the view that the Gattendorfia Stufe was older than the Wockluneria Stufe.

Schindewolf (1926b: 92) then explained that after writing his article on the ammonoid assemblages of Saalfeld ( Schindewolf 1924), he had the opportunity to study the Devonian–Carboniferous boundary section near Wocklum in the Rhenish Mountains in greater detail. During this visit he realised that the Gattendorfia Stufe is not older but younger than the Wockluneria Stufe.

Schindewolf (1952: 297) discussed again his previously established third species “ Gattendorfia involuta Schindewolf, 1924 ”. In this discussion, he stated that this species had no valid name and that he would refer to it as the new species Gattendorfia tenuis . In this article, he described and illustrated a specimen of 73 mm diameter from Saalfeld as the type for that species. He also said that he had previously owned excellently preserved specimens from Oberrödinghausen in the Rhenish Mountains and Ebersdorf (Dzikowiec) in Silesia. A rather well-preserved specimen from Ebersdorf, collected by Schindewolf in 1918 and described as Gattendorfia tenuis by Weyer (1965. 447), belongs to the new species G. schmidti sp. nov. described here. From what has already been said above, it is clear that these specimens Schindewolf mentioned did not belong to the type series.

Vöhringer (1960: 153) used the species name G. tenuis for specimens from Oberrödinghausen, which however belong to three different species. He presented a specimen with a diameter of 57 mm as a photograph and also cross sections of two other, smaller specimens. The assignment of his large specimen to G. tenuis is astonishing, because this specimen deviates considerably from the holotype in the direction of the constrictions. Nevertheless, this concept was accepted by Korn (1994, 2006).

Becker (in Becker et al. 2021: 409) saw the need to revive the hitherto unused species name “ Gattendorfia involuta Schindewolf, 1924 ” and designated specimen GPIT-PV-63952, illustrated by Vöhringer (1960: pl. 5 fig. 6) as G. tenuis , as the neotype for “ G. involuta ”. However, this procedure is to be criticised for several reasons:

1. The neotype does not come from the type region. The claim by Becker that Schindewolf possessed syntypes from Oberrödinghausen (and that this is one of the two type localities) is not correct (see above), since Schindewolf only carried out extensive studies in the Rhenish Mountains Devonian– Carboniferous boundary sections after writing his 1924 article.

2. With the determination of a neotype from another region, the species “ G. involuta ” would become a widespread species by definition, but not by empirical data.

3. The same is true for the stratigraphic range of the species. All ammonoid specimens from Gattendorf come from the lowest part of the Gattendorfia Limestone (regional Acutimitoceras acutum Zone ), while the “ neotype ” comes from the highest bed of the Gattendorfia Limestone ( Eocanites delicatus Zone ). With the neotype proposal, Gattendorfia involuta would become a long-ranging species by definition, not by empirical data.

4. The determination of a neotype is unnecessary, because a specimen of “ G. involuta ” personally labelled by Schindewolf is present in the collection of the Museum für Naturkunde, Berlin; this specimen was probably taken by him when he moved from Marburg to Berlin in 1927.

5. The illustration of another supposedly “typical” specimen by Becker (in Becker et al. 2021: text-fig. 15) adds to the confusion. The poorly preserved specimen is from the basal bed of the Hangenberg Limestone, while the proposed neotype is from the highest bed of the unit. The specimen cannot be considered typical at all because it does not seem to have constrictions like the proposed neotype.

The new species Gattendorfia schmidti sp. nov. is based on a specimen found by Vöhringer and named by him as G. tenuis . Vöhringer stated that he had 22 specimens of this species; of these he sectioned several specimens and illustrated two of them. However, these two differ in their growth trajectories and are attributed here to other species ( G. bella sp. nov., G. valdevoluta sp. nov.). Gattendorfia schmidti differs from G. tenuis in the course of growth lines and constrictions, which in G. schmidti are concavo-convex and form a ventrolateral projection, whereas in G. tenuis they run with a convex curve across the flanks and merge continuously into the ventral sinus. In addition, the constrictions in G. tenuis are limited to the outer half of the flank and the venter, whereas in G. schmidti they already begin at the umbilicus. Gattendorfia schmidti has a stouter conch than G. tenuis ; the ww/dm ratio is about 0.40 in G. schmidti but only 0.32 in G. tenuis .

Figures

Fig. 74. Gattendorfia schmidti sp. nov. from the Oberrödinghausen railway cutting. A. Holotype GPIT- PV-63952 (Vöhringer Coll.) from bed 1. B. Paratype MB.C.31157.1 (Vöhringer Coll.) from bed 3c. Scale bar units= 1 mm.

Fig. 75. Gattendorfia schmidti sp. nov. from the Oberrödinghausen railway cutting. A. Cross section of paratype MB.C.31156.1 (Vöhringer Coll.) from bed 2. B. Cross section of paratype MB.C.31157.2 (Vöhringer Coll.) from bed 3c. C. Suture line of holotype GPIT-PV-63952 (Vöhringer Coll.) from bed 1, at ww =16.5 mm, wh=9.5 mm.D. Constriction course of holotype GPIT-PV-63952 (Weyer 1993–1994 Coll.) from bed 1, at ww =16.5 mm, wh =9.5 mm. E–G. Ontogenetic development of the conch width index (ww/dm), umbilical width index (uw/dm), whorl width index (ww/wh) and whorl expansion rate (WER) of selected specimens. Scale bar units =1 mm.